Blood purification systems, which are used for conducting hemodialysis, hemodiafiltration or hemofiltration, involve the extracorporeal circulation of blood through an exchanger having a semi-permeable membrane. Such systems further include a hydraulic system for circulating blood and a hydraulic system for circulating replacement fluid or dialysate comprising certain blood electrolytes in concentrations close to those of the blood of a healthy subject.
A common problem with all dialysis systems is the accurate detection, and alarming of, an occlusion. In the course of a dialysis treatment, blood is extracted from a patient, through a blood flow circuit that contains a dialyzer, and back to the patient. Flow through the blood circuit may, at times, become occluded by an increased concentration of gasses, coagulation, or various other blood components. An occlusion not only inhibits effective dialysis but can also be dangerous if not detected immediately and cleared.
In cases of an occlusion in the arterial line, or blood circuit, transporting a patient's blood to a dialyzer, an accumulation of gasses may lead to the formation of bubbles. U.S. Pat. No. 9,320,843 discloses “a device for monitoring an extracorporeal blood circuit in which a blood pump is disposed to convey blood, comprising: an apparatus adapted to detect an occurrence of air bubbles in blood that flows in the extracorporeal blood circuit, an apparatus adapted to measure a negative pressure in the extracorporeal blood circuit upstream of the blood pump, and a processing unit programmed to deduce a first defective condition when the apparatus adapted to detect the occurrence of air bubbles in the extracorporeal blood circuit detects air bubbles and the measured negative pressure is above a predetermined limit value for the negative pressure, and/or a second defective condition when the apparatus adapted to detect the occurrence of air bubbles in the extracorporeal blood circuit detects air bubbles and the measured negative pressure is below the predetermined limit value for the negative pressure, wherein the first defective condition differs from the second defective condition.”
U.S. Pat. No. 8,465,641 discloses “a dialysis liquid circuit comprising: conduits for conducting a dialysis liquid, and elements for continuously detecting air in the dialysis liquid and leakage in the dialysis liquid circuit, the elements including at least one gas sensor traversed continuously by dialysis liquid, the at least one gas sensor being configured such that it measures at least one property of the dialysis liquid which depends on the presence of air bubbles in the dialysis liquid, and being arranged downstream of a region to be monitored of the dialysis liquid circuit in which during operation of the dialysis liquid circuit a negative pressure exists with respect to atmospheric pressure, and an evaluation unit which is connected with the gas sensor and is configured such that the property measured via the gas sensor is evaluated with regard to the presence of air bubbles in the dialysis liquid and based thereon, with regard to the presence of leakage in the dialysis liquid circuit.”
While prior art systems have used pressure sensors to generally detect pressure changes and generate alarms or shut down dialysis procedures, they still suffer from excessively high false alarm rates. There remains a need for an improved occlusion detector that can reliably detect an occlusion in a blood circuit but not falsely alarm and unnecessarily cause a dialysis treatment to prematurely terminate.